Radio Communications System, Base Station Apparatus And Method Of Transmission Power Control

ABSTRACT

A transmission power of a communication apparatus can be appropriately determined in accordance with different communication multiplicities between two or more communication channels. A mobile communication system in which a base station apparatus and a mobile station apparatus communicate with each other by using configuration channels (CCH) or random access channels (RACH) includes a transmission power control part for determining basic data of the transmission power in RACH of the mobile station apparatus in accordance with a communication status in CCH, and a transmission power determining part for determining the transmission power in RACH of the mobile station apparatus by changing the basic data at least in accordance with the communication multiplicity of RACH.

TECHNICAL FIELD

This invention relates to a radio communications system, a base stationapparatus and a method of the transmission power control.

BACKGROUND ART

In radio communications, there are cases where two or more communicationchannels with different communication multiplicities could be used forradio communications. For example, some mobile communication systemssuch as PHS (Personal Handyphone System) adopting the SDMA (SpaceDivision Multiple Access) method use two logical channels which are CCH(Configuration Channels) and RACH (Random Access Channels). In CCHcommunications multiplexing by spatial multiplexing are not performed,and in RACH communications multiplexing by spatial multiplexing areperformed.

Here, the patent document 1 discloses a patent related to a method forthe power control in wireless networks.

Patent document 1: EP Patent Application No. 0741467

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention

When communications are started in the aforementioned mobilecommunication systems, synchronous processes between base stationapparatus and mobile station apparatus, registration processes, etc. areto be processed in CCH. Then next, channel allocation processes etc. areto be processed in RACH. In these cases, the transmission power controlof the mobile station apparatus is performed by an open loop control.Later, the communications begin in traffic channels, and then thetransmission power control is performed by a closed loop control.

Therefore, the results of the open loop control in CCH will be reflectedon the signal transmission in RACH. However, in many cases the noiselevels of RACH and CCH are different because of the different spatialmultiplicities between RACH and CCH, so that a good communication resultcould not be obtained even though the result of the open loop control inCCH is reflected on the communications in RACH. That is, thetransmission power of mobile station apparatus have not beenappropriately controlled in accordance with the different communicationmultiplicities between two or more communications channels, thusaffecting the communication result.

The present invention is proposed based on a consideration of the aboveproblem. The purpose is to provide a radio communications system, a basestation apparatus and a method of transmission power control which allowappropriate determination of a transmission power of a communicationapparatus in accordance with different communication multiplicitiesbetween two or more communication channels.

Means for Solving the Problem

In order to solve the above problem, the present invention provides aradio communications system including a plurality of communicationapparatuses, comprising a first communication device which a firstcommunication apparatus and a second communication apparatus communicatewith each other by using a first communication channel, a secondcommunication device which the first communication apparatus and thesecond communication apparatus communicate with each other by using asecond communication channel, a transmission power basic data determinerwhich determines basic data of the transmission power in the secondcommunication channel of the second communication apparatus inaccordance with a communication status in the first communicationchannel, and a transmission power determiner which determines thetransmission power in the second communication channel of the secondcommunication apparatus by changing the determined basic data of thetransmission power at least in accordance with the communicationmultiplicity of the second communication channel.

By doing this, the transmission power of the communication apparatus canbe appropriately determined in accordance with different communicationmultiplicities between two or more communication channels.

In addition, in the aforementioned radio communications system, thetransmission power determiner may change the determined basic data ofthe transmission power further in accordance with the communicationmultiplicity of the first communication channel.

Further, in the aforementioned radio communications system, thetransmission power determiner may determine the transmission power inthe second communication channel of the second communication apparatusin such a way that the higher the communication multiplicity of thesecond communication channel, the greater this transmission power.

Moreover, in the aforementioned radio communications system, at leastthe communication multiplicity in the second communication channel maybe a spatial multiplicity.

In addition, a base station apparatus according to the present inventionis a base station apparatus used in a mobile communication system,including a first communication device for communicating with a mobilestation apparatus by using the first communication channel, a secondcommunication device for communicating with the mobile station apparatusby using the second communication channel, and a transmission powerdeterminer which determines the amount of change in the basic data oftransmission power determined by a transmission power basic datadeterminer at least in accordance with the communication multiplicity ofthe second communication channel.

Further, a transmission power control method according to the presentinvention includes a first communication step in which a firstcommunication apparatus and a second communication apparatus communicatewith each other by using a first communication channel, a secondcommunication step in which the first communication apparatus and thesecond communication apparatus communicate with each other by using asecond communication channel, a step of determining basic data of thetransmission power in the second communication channel of the secondcommunication apparatus in accordance with a communication status in thefirst communication channel, and a step of determining the transmissionpower in the second communication channel of the second communicationapparatus by changing the determined basic data of the transmissionpower at least in accordance with the communication multiplicity of thesecond communication channel.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a configuration diagram of a mobile communication systemaccording to an embodiment of the present invention.

FIG. 2 is a configuration block diagram of a mobile station apparatusaccording to an embodiment of the present invention.

FIG. 3 is a configuration block diagram of a base station apparatusaccording to an embodiment of the present invention.

FIG. 4 is a functional block diagram of a base station apparatusaccording to an embodiment of the present invention.

FIG. 5 is a sequence diagram of a mobile communication system accordingto an embodiment of the present invention.

FIG. 6 is a functional block diagram of a mobile communication systemaccording to an embodiment of the present invention.

FIG. 7 is a process flowchart of a base station apparatus according toan embodiment of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

Referring to drawings, an embodiment of the present invention isdescribed hereinafter.

As shown in FIG. 1, a mobile communication system 4 according to thisembodiment is configured with a plurality of mobile station apparatuses1, a base station apparatus 2, and a communication network 3. The basestation apparatus 2 typically communicates with the communicationnetwork 3 and each of the mobile station apparatuses 1.

As shown in FIG. 2, the mobile station apparatus 1 includes a controlpart 11, a communication part 12, a memory part 13, an operating part14, and a display part 15. The control part 11 controls each part of themobile station apparatus 1 and performs processes related to telephonecalls and data communications. The communication part 12, which hasantennas, performs processes such as modulating audio signals,communication packets, etc. and then transmitting through the antennasin accordance with instructions provided by the control part 11, andreceiving and demodulating audio signals, communication packets, etc.arriving at the antennas and then outputting to the control part 11. Thememory part 13 operates as a work memory for the control part 11. Thismemory part 13 also holds programs and parameters for various processesperformed by the control part 11. The operating part 14 is, for example,a numeric keypad etc. for receiving phone numbers and character stringsinput from users and outputting to the control part 11. The display part15 is, for example, composed of a liquid crystal display, which displaysinformation in accordance with an input from the control part 11.

As shown in FIG. 3, the base station apparatus 2 includes a control part21, a network interface part 22, a radio communications part 23, and amemory part 24. The control part 21 controls each part of the basestation apparatus 2 and performs processes related to telephone callsand data communications. The network interface part 22, which isconnected to the communication network 3, receives audio signals,communication packets, etc. and outputs to the control part 21, and alsotransmits audio signals, communication packets, etc. to thecommunication network 3 in accordance with instructions from the controlpart 21. The radio communication part 23, which has antennas, performsprocesses such as receiving and demodulating audio signals,communication packets, etc. from each of the mobile station apparatuses1 and then transmitting to the control part 21, and modulating audiosignals, communication packets, etc. provided by the control part 21 andthen transmitting through the antennas in accordance with instructionsprovided by the control part 21. The memory part 24 operates as a workmemory for the control part 21. This memory part 24 also holds programsand parameters for various processes performed by the control part 21.

In terms of the functionality, the radio communications part 23 and thecontrol part 21 of the base station apparatus 2, as shown in FIG. 4,includes a plurality of transmitting/receiving parts 30, a path controlpart 32, a signal processing part 34. Each transmitting/receiving part30 has an antenna 36. This plurality of antennas 36 constitute aconventionally well-known adaptive array antenna. A process performed bythis configuration is briefly described hereinafter. In the receivingprocess, each antenna 36 receives audio signals, communication packets,etc. arriving at the antenna. Each transmitting/receiving part 30converts the frequency of the received radio wave supplied from eachantenna 36 and then outputs to the path control part 32. The pathcontrol part 32 routes the output from each transmitting/receiving part30 to the signal processing part 34 which performs the demodulatingprocess and decoding process. The signal processing part 34 obtainsreceived signals based on the correlation between the signals suppliedfrom the path control part 32 and the reference signals. Receiving radiowaves by using the plurality of antennas 36 in this way, the basestation apparatus 2 can obtain the received signals from each of themobile station apparatuses 1 correctly even if fading occurs.

In the transmitting process, on the other hand, the signal processingpart 34 determines the antenna weight of each antenna for each of themobile station apparatuses 1 as destination based on the receivedsignals. Each antenna weight is a weight of the transmission power ofthe signal transmitted from each antenna 36 to the mobile stationapparatuses 1. Each transmitting/receiving part 30 then transmitssignals from each antenna 36 based on the antenna weight. Electricallycontrolling each weight of the transmission power in this way, the basestation apparatus 2 can emit electromagnetic waves with directivity.

Thus, in the mobile communication system 4 applying an adaptive arrayantenna can perform communications with high directivity between each ofthe mobile station apparatuses 1 and the base station apparatus 2.Therefore, the base station apparatus 2 can communicate with each theplurality of mobile station apparatuses 1 at the same frequency at thesame time. Such communications are referred to as “spatiallymultiplexed”. For example, the SDMA method is known as this kind ofcommunication method.

In the mobile communication system 4, it is controlled so that thereceived signal strength at the base station 2 of the radio wavetransmitted from each of the mobile station apparatuses 1 may alwaysbecome equal. This is because in an uplink (a transmission from themobile station apparatus 1 to the base station apparatus 2) the fartherthe mobile station apparatus 1 is from the base station apparatus 2, thelower the received signal strength becomes, and the closer these twostations are, the higher the received signal strength becomes. Then theradio waves from the plurality of mobile station apparatuses 1 whichcommunicate with the base station apparatus 2 may interfere with eachother. Particularly radio waves which are strong in the received signalstrength may cause interference with radio waves which are weak in thereceived signal strength, and therefore a demodulation at the basestation apparatus 2 may be affected. In a case like this, the number ofmultiple access within the same time slot needs to be reduced in orderto improve the accuracy of the demodulation, causing a lowering of thetotal throughput.

More concretely, the mobile communication system 4 performs atransmission power control in coordination with each communicationenvironment, for example, by an open loop control in BCH (BroadcastChannel), CCH and RACH, and a closed loop control in TCH (TrafficChannel), coordinating the transmission power so that a demodulatablecertain level of SINR (Signal-to-Interference Noise Ratio) can beobtained. In addition, it is intended to improve the communicationquality by selecting an appropriate modulation class by the linkadaptation.

The aforementioned open loop control is performed through BCH, CCH, andRACH. However, the process in BCH and CCH is performed either in adifferent carrier or different time slot from those of RACH and TCH.Concretely, spatial multiplexing is used in RACH and TCH, while spatialmultiplexing is not used in BCH and CCH. For example, when using thespatial multiplexing method in which one time slot is used by threecommunications, a transmission power obtained by the open loop controlin BCH and CCH may not meet the communication environment of RACH andTCH. This is because there are cases where each value of the noiselevels which form a noise floor inherent in a time slot is differentfrom each other due to the different spatial multiplicities between BCH& CCH and RACH & TCH. In general, the higher the spatial multiplicity,the greater the noise floor becomes because of an effect of theinterference wave from the mobile station apparatuses 1 which arespatially multiplexed in the same time slot. Therefore, with thetransmission power determined by the open loop control in BCH and CCH,the received signal strength at the base station apparatus 2 issometimes too small to demodulate the signal.

This embodiment of the present invention makes it possible toappropriately determine the transmission power of a communicationapparatus in accordance with different communication multiplicities oftwo or more communication channels by using communication multiplicitiesrepresented by the above spatial multiplicities as one of the parametersto determine the transmission power in the open loop control. A concreteconfiguration to make communication multiplicities one of the parametersto determine the transmission power in the open loop control isdescribed hereinafter.

In a mobile communication system 4 communication is established in asequence shown in FIG. 5, when a base station apparatus 2 and a mobilestation apparatus 1 start the communication. First the mobile stationapparatus 1 receives a BCH broadcasted from the base station apparatus 2and then performs processes such as determining a base station apparatus2 to be its communication counterpart and confirming synchronization.Then the mobile station apparatus 1 uses CCH to perform determination ofthe transmission power, establishment of synchronization anddetermination of the channel for the base station apparatus 2 determinedas a communication counterpart. In CCH a signal transmitted from amobile station apparatus 1 to a base station apparatus 2 is called a“configuration request” (CR) and a signal transmitted from a basestation apparatus 2 to a mobile station apparatus 1 is called a“configuration message” (CM). The transmission power used in this phaseis determined by the mobile station apparatus 1 in accordance with areceived signal strength of BCH or CM at the mobile station apparatus 1.This means that the mobile station apparatus 1 can determine how muchtransmission power is necessary to make the radio wave transmitted byitself to reach the base station apparatus 2 based on the receivedsignal strength of the BCH and CM, since the transmission power of thebase station apparatus 2 is constant. This process of transmission powercontrol is called “open loop control”.

Then, call registration, channel allocation, etc. are processed by usingRACH. This means that processes to start a call processing areperformed. In RACH a signal transmitted from a mobile station apparatus1 to a base station apparatus 2 is called a “request access” (RA) and asignal transmitted from a base station apparatus 2 to a mobile stationapparatus 1 is called an “access assignment” (AA). When the processcompletes in RACH, the call is established and then communication startsin the data channel (not shown in figures). Once call processing startsin the data channel, the transmission power control is performed byreceiving a reception status of the communication counterpart'sapparatus. This process of transmission power control is called “closedloop control”. Here a logical channel which performs controls such asBCH, CCH and RACH and others is called a “control channel”. In addition,a logical channel such as a data channel is called a “traffic channel”.

As described above, communications in the first communication channelrepresented by BCH and CCH, and communications in the secondcommunication channel represented by RACH are performed using differentphysical channels. Thus, the second communication channel allows thebase station apparatus 2 to determine the antenna weight based on theradio wave transmitted by each of the mobile station apparatuses 1 andthen allow spatial multiplexing, while the first communication channeldoes not allow spatial multiplexing since the base station apparatus 2does not know the location of each of the mobile station apparatuses 1.In other words, the first communication channel and the secondcommunication channel have different communication multiplicities. Thesecond communication channel will start to be used after the firstcommunication channel. The initial transmission power of the mobilestation apparatus 1 in the second communication channel will be thetransmission power determined by the open loop control in the firstcommunication channel.

Differing from the first communication channel, the communications inthe second communication channel are multiplexed. This means that itcould suffer from interference with radio waves used by other mobilestation apparatuses 1 which are multiplexed counterparts. Therefore,depending on the degree of the interference, signals particularly in thesecond communication channel may not be modulated or demodulated at thebase station apparatus 2 without increasing its transmission power. Thusin the open loop control which determines the transmission power inaccordance with the communication status in the first communicationchannel, not only is the communication status in the secondcommunication channel unknown, but also the mobile station apparatus 1does not know the interference status at the base station apparatus 2,and so the mobile station apparatus 1 cannot perform an appropriatetransmission power control and the base station apparatus 2 may not beable to modulate or demodulate received signals in some cases. In orderto prevent this, the mobile communication system 4 determines thetransmission power of the mobile station apparatus 1 in accordance withthe communication multiplicity in the base station apparatus 2. FIG. 6shows a concrete functional block diagram of a mobile communicationsystem 4.

A mobile station apparatus 1 in this embodiment is functionally composedof a receiving part 60, a transmission power control part 62 and atransmitting part 64. A mobile station apparatus 2 is functionallycomposed of a receiving part 50, a control part 52, a communicationmultiplicity acquiring part 54, a transmission power determining part 56and a transmitting part 58.

The receiving part 50 receives a radio wave from a mobile stationapparatus 1 and outputs to the control part 52. Then the control part 52in turn executed processing to perform communications multiplexing suchas, for example, a calculation of antenna weight in regards to spatialmultiplexing when communication in the second communication channel isperformed as a next step. The communication multiplicity acquiring part54 acquires a communication multiplicity, which is the number of mobilestation apparatuses 1 which are multiplexed in the second communicationchannel by the control part 52. The communication multiplicity acquiringpart 54 outputs the acquired communication multiplicity to thetransmission power determining part 56 and then the transmission powerdetermining part 56 determines the amount of change in the transmissionpower of the mobile station apparatus 1 based on this communicationmultiplicity. Since the higher the communication multiplicity of thesecond communication channel is, the greater the above describedinterference typically becomes, the above amount of change may bedetermined so that the higher the communication multiplicity of thesecond communication channel is, the greater the transmission power ofthe first mobile station apparatus 1 becomes.

Once a process by the closed loop control begins, the amount of changein this transmission power is not required. Therefore it is consideredthat an increase in a transmission power of other mobile stationapparatuses 1 will hardly occur by this process at the same time in theevent of an increase in the transmission power of the mobile stationapparatus 1. Thus an effect on the call process by the increasedinterference caused by the rising transmission power in this process isconsidered to be negligible.

Then the transmission power determining part 56 outputs to thetransmitting part 58 the above amount of change in the transmissionpower of the mobile station apparatus 1, and in turn the transmittingpart 58 transmits this amount of change to this mobile station apparatus1.

The mobile station apparatus 1 receives this amount of change at thereceiving part 60 and outputs to the transmission power control part 62.Here the transmission power control part 62 measures a communicationstatus of a received signal (e.g. transmission loss) in the firstcommunication channel and determines the basic data of the transmissionpower in the first communication channel and as well as the transmissionpower in the second communication channel of the mobile stationapparatus 1 in accordance with the measured communication status (Openloop control). The transmission power control part 62 changes the basicdata of the transmission power by adding this amount of change providedby the receiving part 60 to the basic data of the transmission power inthe second communication channel determined by the open loop control,thus determining the transmission power, and then outputs the determinedtransmission power to the transmitting part 64. The transmitting part 64then performs a transmission in the second communication channel at thisprovided transmission power.

The transmission power determining part 56 does not only determine theabove amount of change in accordance with the communication multiplicityin the second communication channel as in the above process, but mayalso be configured to determine the above amount of change in accordancewith the communication multiplicity in the first communication channel.That means, that although the configuration of the above example doesnot adopt a communication multiplicity in the first communicationchannel, it is clearly seen that a communication multiplicity may beperformed in the first communication channel in some cases. In thiscase, in order to more appropriately reflect the difference betweeninterferences caused by the communications multiplexing in the firstcommunication channel and the second communication channel, it isdesirable to determine the transmission power of the mobile stationapparatus 1 in the second communication channel in accordance with thedifference or ratio between the communication multiplicities in thefirst communication channel and the second communication channel.

Referring to a flowchart the aforementioned process is further describedin detail.

FIG. 7 shows a detailed flowchart of the process of a base stationapparatus 2 in an embodiment of the present invention. The maximumcommunication multiplicity in this flowchart is set to 3. It is clearlyunderstood that it can be applicable to various communicationmultiplicities in practice. First, a base station apparatus 2 transmitsa BCH (S100). Then a mobile station apparatus 1 calculates downstreamtransmission loss (S100). This downstream transmission loss will also beused for an open loop control in the mobile station apparatus 1. Thismeans that the mobile station apparatus 1 uses the downstreamtransmission loss as a communication status and can determine thetransmission power or the basic data of the transmission power of thismobile station apparatus 1 in accordance with this communication status.Secondly, a CR is received in CCH (S102). Here the base stationapparatus 2 calculates a correction value to correct the transmissionpower of this base station apparatus 2 based on the downstreamtransmission loss information included in this CR (S102). Thiscorrection is a process for determining the transmission power of thebase station apparatus 2 by open loop control.

Then the base station apparatus 2 judges whether or not the number ofusers already communicating in the physical channel used in the RACH isone (S104). This number of users is, in other words, the communicationmultiplicity. The base station apparatus 2 determines the value of K1when this number of users is one (S106). If the number of users is notone, the base station apparatus 2 judges whether or not the number ofusers already communicating in the physical channel used in the RACH istwo (S108). If the number of the users is two, the base stationapparatus 2 determines the value of K2 (S110). Here, K1 is the amount ofchange in the transmission power with which the mobile station apparatus1 is transmitting a RA in the case that the communication multiplicityis 1. K2 is the amount of change in the transmission power with whichthe mobile station apparatus 1 is transmitting a RA in the case that thecommunication multiplicity is 2. Thus the base station apparatus 2determines the amount of change in the transmission power of the mobilestation apparatus 1 in accordance with the communication multiplicity inthis base station apparatus 2. Then, the base station apparatus 2transmits a CM in CCH (S112). At this time, the base station apparatus 2can transmit this CM including K1 and K2. In this way, the base stationapparatus 2 informs the mobile station apparatus 1 of the amount ofchange in the transmission power. The base station apparatus 2 maytransmit either K1 or K2 required in accordance with the communicationmultiplicity. In addition the base station apparatus 2 may be configuredto transmit information indicating this amount of change and the mobilestation apparatus 1 may be configured to acquire the amount of change byreading the amount of change recorded in, for example, the memory part13 based on the information indicating this amount of change.

The mobile station apparatus 1 determines a transmission power of the RAbased on this amount of change acquired and the basic data of thetransmission power in RACH of this mobile station apparatus determinedby an open loop control in accordance with the received power of the CMin the mobile station apparatus, and then transmits the RA with thistransmission power. In other words, the mobile station apparatus 1determines a transmission power of the RA by adding this acquired amountof change to the basic data of the transmission power in RACH of thismobile station apparatus determined by an open loop control inaccordance with the received power of the CM in the mobile stationapparatus. Then the base station apparatus 2 receives this RA in RACH,and again calculates a correction value to correct the transmissionpower of the base station apparatus 2 based on the downstreamtransmission loss information included in this RA (S114). Then, the basestation apparatus 2 transmits an AA with this corrected transmissionpower in RACH (S116).

More concretely, a transmission power of the mobile station apparatus 1can be determined using the following equations. In the followingequations, P′ represents basic data and P represents a transmissionpower of a mobile station apparatus 1. Equation 1 represents the casewhere the multiplicity is 1, Equation 2 represents the case where themultiplicity is 2, and Equation 3 represents the case where themultiplicity is 3. Therefore the transmission power control part 62 ofthe mobile station apparatus 1 adds the amount of change which isdetermined by the transmission power determining part 56 of the basestation apparatus 2 corresponding to the communication multiplicity, tothe basic data. Moreover this amount of change is recorded correspondingto the communication multiplicity, and so it can be determined byreading out this communication multiplicity recorded in accordance withthe communication multiplicity, or these functions are recorded asfunctions of the communication multiplicity and this amount of changecan be determined by calculations which apply these functions to thecommunication multiplicity.

P=P′  [Equation 1]

P=P′+K1  [Equation 2]

P=P′+K2  [Equation 3]

As described above, a transmission power of the mobile station apparatus1 can be appropriately determined in accordance with the spatialmultiplicity. Particularly, by appropriately determining thetransmission power of the mobile station apparatus 1 in the secondcommunication channel, the base station apparatus 2 can ensure thereception in the second communication channel. Moreover, in atransmission power control and a link adaptation which can improve thecommunication quality between a base station apparatus 2 and a mobilestation apparatus 1, by controlling the transmission power intransmitting/receiving time-shared data and adopting an appropriatemodulation class, the transition from open loop control to closed loopcontrol can be facilitated. In addition, since a reconnection after adisconnection of TCH is facilitated, the throughput of thecommunications will be improved.

1. A radio communications system including a plurality of communicationapparatuses, comprising: a first communication device which a firstcommunication apparatus and a second communication apparatus communicatewith each other by using a first communication channel; a secondcommunication device which the first communication apparatus and thesecond communication apparatus communicate with each other by using asecond communication channel; a transmission power basic data determinerwhich determines basic data of a transmission power in the secondcommunication channel of the second communication apparatus inaccordance with a communication status in the first communicationchannel; and a transmission power determiner which determines thetransmission power in the second communication channel of the secondcommunication apparatus by changing the determined basic data of thetransmission power at least in accordance with a communicationmultiplicity of the second communication channel.
 2. A radiocommunications system according to claim 1, wherein the transmissionpower determiner changes the determined basic data of the transmissionpower further in accordance with a communication multiplicity of thefirst communication channel.
 3. A radio communications system accordingto claim 1 or 2, wherein the transmission power determiner determinesthe transmission power in the second communication channel of the secondcommunication apparatus in such a way that the higher the communicationmultiplicity of the second communication channel, the greater thistransmission power.
 4. A radio communications system according to claim1 or 2, wherein at least the communication multiplicity in the secondcommunication channel is a spatial multiplicity.
 5. A base stationapparatus used in a mobile communication system, comprising: a firstcommunication device for communicating with a mobile station apparatusby using a first communication channel; a second communication devicefor communicating with the mobile station apparatus by using a secondcommunication channel; and a transmission power determiner whichdetermines the amount of change in basic data of a transmission powerdetermined by a transmission power basic data determiner at least inaccordance with a communication multiplicity of the second communicationchannel.
 6. A transmission power control method, comprising: a firstcommunication step in which a first communication apparatus and a secondcommunication apparatus communicate with each other by using a firstcommunication channel; a second communication step in which the firstcommunication apparatus and the second communication apparatuscommunicate with each other by using a second communication channel; astep of determining basic data of a transmission power in the secondcommunication channel of the second communication apparatus inaccordance with a communication status in the first communicationchannel; and a step of determining the transmission power in the secondcommunication channel of the second communication apparatus by changingthe determined basic data of the transmission power at least inaccordance with a communication multiplicity of the second communicationchannel.